After more power from a Boosted 355

[skyracer]

So car is booked in for some more tuning, want to get a bit more power out of it. 265rwkw is nice but I would prefer a nice round 300rwkw or 330rwkw. Pondering what mods I can do to achieve this without going all out like cam and springs, pistons and rods ect??? The engine is pretty much stock sooo

As it is now:
Engine - Stock 5.7L Holden Harrop Stroker, upgraded fuel system. Ac removed.
Exhaust - HPC Pacemaker Tri Y's into High flow cats, High flow mufflers, 2 1/2 twin system all the way with a resonator on the end.
Boost - V2 Vortech supercharger with intercooler running 10 psi

Ideas please

Twin Throttle manifold
larger throttle body
Higher ratio rockers
Electric csr water pump

What kind of power gains (if any) Would I be expecting from these mods? Worth it? Not worth it?

Not sure what else I can do? Help!

[Not_An_Abba_Fan]

You can fit tuned length 4-1 extractors and twin 3" which will give you more kW's but no more torque.

You can tweak the tune to give you a bit more too. 265rwkw on a supercharged stroker is not that impressive....What's your torque figure like? I bet it's high, but low in the revs.

[Aussiepride5L]

So car is booked in for some more tuning, want to get a bit more power out of it. 265rwkw is nice but I would prefer a nice round 300rwkw or 330rwkw. Pondering what mods I can do to achieve this without going all out like cam and springs, pistons and rods ect??? The engine is pretty much stock sooo

As it is now:
Engine - Stock 5.7L Holden Harrop Stroker, upgraded fuel system. Ac removed.
Exhaust - HPC Pacemaker Tri Y's into High flow cats, High flow mufflers, 2 1/2 twin system all the way with a resonator on the end.
Boost - V2 Vortech supercharger with intercooler running 10 psi

Ideas please

Twin Throttle manifold
larger throttle body
Higher ratio rockers
Electric csr water pump

What kind of power gains (if any) Would I be expecting from these mods? Worth it? Not worth it?

Not sure what else I can do? Help!

All of the above at the moment mate. The higher ratio rockers will help act like a bit bigger cam, and the larger plenum will get more air in...more air = more fuel = more power..!!!
Depending on what manifold you have will be the key. If you bought a Starr or a C.O.M.E (or copy) this will definitely help...especially with a 90mm single throttlebody. Also putting in a front mount intercooler will help too...and if I had a vortec as opposed to a twinscrew, it will definitely make a difference.

Maximise your induction, then retune and Im sure you'll punch 300wrkw. You might have to adjust your drive pulley size on the blower as well to spool a little later for the rocker-timing change.

As ol' mate said... 265kw is abit sub from a Blown 355...!!

[skyracer]

Thanks guys,

It pulled 1077nm of torque. The car had a run on the dyno before I put the charger on it. Made 156rwkw with 438nm. It's the stock stroker holden came out with back in the day. 215i Model. After a bit of reading I don't think they are a true 355? not too sure. Think the harrop cranks they used only stroked them out to 350 or so. So that the did not have to cut bits out of the block to accommodate the throw of the crank. Anyway it is a 16 year old engine so I was happy with the 110rwkw gain from the charger. Not like it was a 355 stroker kit from come racing with low comp pistons or something. Then I would have been expecting more horses haha

Was thinking of the C.O.M.E Racing twin Throttle manifold. They have a deal on, everything for $2000. Couple that with some YT high ratio rockers and CSR Electric water pump (not that the pump will free up anything, maybe like 1HP but still nice to have). Would hope to be getting a extra 35rwkw out of that? Or am I dreaming... lol

[crazybiker]

Thanks guys,

It pulled 1077nm of torque. The car had a run on the dyno before I put the charger on it. Made 156rwkw with 438nm. It's the stock stroker holden came out with back in the day. 215i Model. After a bit of reading I don't think they are a true 355? not too sure. Think the harrop cranks they used only stroked them out to 350 or so. So that the did not have to cut bits out of the block to accommodate the throw of the crank. Anyway it is a 16 year old engine so I was happy with the 110rwkw gain from the charger. Not like it was a 355 stroker kit from come racing with low comp pistons or something. Then I would have been expecting more horses haha

Was thinking of the C.O.M.E Racing twin Throttle manifold. They have a deal on, everything for $2000. Couple that with some YT high ratio rockers and CSR Electric water pump (not that the pump will free up anything, maybe like 1HP but still nice to have). Would hope to be getting a extra 35rwkw out of that? Or am I dreaming... lol

1077nm?

HOLY JESUS. That's whopping.

[Aussiepride5L]

What size throttle body do you currently have...? And are you running the standard "banana" manifold...? If the answer is yes to both of those then you will see a definite gain by changing them both, but do find out what the highest ratio rockers you can run are and change to them too. The banana manifold chokes the rpms down. Once you maximise your induction and retune the car will be totally different. Your torque figues are sweet... its just the flow for hp that is affected. Once you have changed everything and are off to the tuners, make sure they have spare pulleys there to change your boost window as well. My mate has a 355 with a 2.5LWhipple twinscrew charger. He makes the same torque as you but 615rwhp.

[skyracer]

Yep, standard throttle body with the banana manifold. Sounds like changing them is the way to go!

Also do you know what mods your mate has? That's awesome HP!!!

How much boost?
Crank?
Rods?
Pistons and what comp?
Heads worked?
cam?

Those whipple chargers really are amazing...

[Aussiepride5L]

Yep, standard throttle body with the banana manifold. Sounds like changing them is the way to go!

Also do you know what mods your mate has? That's awesome HP!!!

How much boost?
Crank?
Rods?
Pistons and what comp?
Heads worked?
cam?

Those whipple chargers really are amazing...

Mate seriously.... you dont even have to put roller rockers on, (but it will add hp) main thing is new manifold, throttlebody and tune and you will fkn jizz your pants....!!! If you are going to put a new cam in then change your heads to ported alloy VN heads or at least port your current heads. They are the next choker-exhaust ports. Where do you stop right...??? How much hp do you really want...???.... exactly. Just do your manifold, throttlebody and tune for now = almost $3k as is, then talk more hp if your still not happy. But I reckon you will be.
My mates 355 is a rollercam engine and was fully worked and dyno'd to 450rwhp pre boost. 10psi later and he's on the upper limit of the safe zone before he puts a piston through the head. He cant run less than 98ron. It demolishes his 275rear tires...!!
Next he will up the stroke to 383....but really..probs wont happen as he has a new missus. XD

[Aussiepride5L]

Im looking for a factory 355 engine block like yours, I'd prefer VT series. You know of any...?

[ari666]

ok: to start with the very first thing you need to do is listen to NAAF and change to 4-1's and get rid of your bananas.

what that will effectively do is bump up your rpm. if you are getting 1000nm of torque but only 265kw it means your running out of puff at higher rpm. the 4-1's and manifold will let you rev higher, which means your torque can be calculated higher, which will give you the theoretical KW figure you are after.

1000nm sounds like tonnes, but if you are getting that at 1600rpm then capping out at 4500 rpm, itll show a really low KW figure. plus its silly to have that tight of a power band. you just wont be able to put it to the road.

i am having doubts that this engine will survive for very long.

[juiceie vh sle]

Thanks guys,

It's the stock stroker holden came out with back in the day. 215i Model. After a bit of reading I don't think they are a true 355? not too sure. Think the harrop cranks they used only stroked them out to 350 or so.

hey mate the factory strokers were only 350ci. the extra 5 cubes in a 355 comes from boring the block .030" oversize. your stroker crank has the same thow but only slightly smaller piston diameter.

[skyracer]

Im looking for a factory 355 engine block like yours, I'd prefer VT series. You know of any...?

Sorry not at the moment.

ok: to start with the very first thing you need to do is listen to NAAF and change to 4-1's and get rid of your bananas.

what that will effectively do is bump up your rpm. if you are getting 1000nm of torque but only 265kw it means your running out of puff at higher rpm. the 4-1's and manifold will let you rev higher, which means your torque can be calculated higher, which will give you the theoretical KW figure you are after.

1000nm sounds like tonnes, but if you are getting that at 1600rpm then capping out at 4500 rpm, itll show a really low KW figure. plus its silly to have that tight of a power band. you just wont be able to put it to the road.

Thanks heaps!

Are there any suppliers that do 4-1's off the shelf for my car? Or would I need to get them custom built?

Love the knowledge you guys have it's awesome!

i am having doubts that this engine will survive for very long.

Why's that? Because I'm trying to push a factory bottom end that has a high comp ratio? I'm open to suggestions.

hey mate the factory strokers were only 350ci. the extra 5 cubes in a 355 comes from boring the block .030" oversize. your stroker crank has the same thow but only slightly smaller piston diameter.

Knew it was something like that, thanks for clearing that up for me.

[Not_An_Abba_Fan]

I think Difillipo do a set of 4-1 tuned length for the VS.

I know Hurricane do a set of 1 3/4" primary "tuned interference" that run tuned length short primaries then into twin long tube secondaries that work very well on forced induction engines.

Then run twin cats and a good twin 2 1/2" system, that will free the exhaust up and push the torque higher up in the revs. With 1000+ nm of torque and only 265 rwkw, you must run out of puff really quickly. According to my calculations, you must be hitting peak torque at around 2500rpm.

[ari666]

Why's that? Because I'm trying to push a factory bottom end that has a high comp ratio? I'm open to suggestions.

just the amount of work its doing with nothing else done to suit. 1000nm is a hell of a lot of load for a stock bottom end. personally i would be babying it untill you know for sure whats underneath. stuff like headgaskets, 4 bolt mains or girdles and high quality bearings will make it live longer and wont cost the earth.

[blo304]

just the amount of work its doing with nothing else done to suit. 1000nm is a hell of a lot of load for a stock bottom end. personally i would be babying it untill you know for sure whats underneath. stuff like headgaskets, 4 bolt mains or girdles and high quality bearings will make it live longer and wont cost the earth.

1000nm is tractive effort.. not even closely an indicator of engine torque if this thing was making 740 ft/lbs at the engine it would be making 400hp at 2,800rpm and the thing would belong in a kenworth lol..

As above sounds like its struggling to breathe. What exhaust do you have at the moment i bet that is what is holding you back there is nothing stopping you getting 300rwkw out of a banana intake and factory rockers if you keep the revs down. Rockers will set you back $600 plus and net you maybe 5hp at the engine at best. Better off investing that in an exhaust if your not going all out at once.

[skyracer]

It has the Pacemaker PH 5002 - COMPETITION HEADER Going into a Twin 2 and a half inch system all the way back, with twin high flow cats and high flow mufflers.

Kind of disappointing if I have to change the exhaust though. Asked the guy to build it to suit the charger, he was like "yeah no probs". Guess I'm not going back to that shop again >.<

High ratio rockers really that pointless in my situation, like bang for buck wise? If so then for now I might just go the twin throttle manifold from C.O.M.E and see how much gain there is.

The car is booked in on the 21st so I have till then to work out exactly what I'm doing. hmmmmmm

[Not_An_Abba_Fan]

Can you post up a pic of the dyno readout? Might be able to see where you have to look for improvements.

[juiceie vh sle]

i would definatly get a cam... if its stock it will be holding back a lot of power

also a COME twin TB manifold if the wallet will go that far but cam first for sure

[Not_An_Abba_Fan]

Maybe it's in your tune, is it the stock Delco ECU?

[blo304]

Sorry i missed the exhaust bit in your first post.. Dont get all hung up on your dyno figures, Are you sure its not just a conservative dyno... run it at the strip.
I would get a small blower cam before blowing 2k on a come manifold.. and an intercooler depending what your intake temps are.. all stuff that will complement a new manifold in the future but probably neccessary at the moment. You just obviously cant slap in a monster cam with the bananas still in place. Its all a juggling act to get everything working together.

If you really wanna see if your exhaust is killing you drop your pipes and do a power run on the dyno straight out the extractors.

[skyracer]

[skyracer]

Thanks for all the info guys and gals if any lol Very much appreciated!!!

Took those photo's with my go pro so there not the best... but its readable.

So given the exhaust work ive already done (waste of money or so it seems lol) The next logical step would be a cam then the manifold? hmmmmmm thinking, thinking...

[Not_An_Abba_Fan]

3rd gear, thats why your torque is so high. I wouldn't base much on that readout at all. I bet it accelerates like a rocket though.

[skyracer]

Yeah I noticed that too, although he did say it was done in 4th gear as that is the 1:1 ratio gear in the t56 6 speed manual. But yeah accelerates like a rocket when I'm not launching it like a gimp and just wheel spinning all the time. My Pedal to clutch ratio is not all that great. LOL

[ari666]

baby jesus curses dyno readings in kmph